Especially as certain strikers are very good at exploiting this, most obviously van Nistelrooy and van Persie who would lurk just offside waiting to be played onside by defenders dropping back as the ball was playedYou are talking about being offside from running ahead of the opponents, but that is not the only way of being offside. After an attack breaks down the forward has to get back onside to receive a pass. The scenario you present ignores this. To be fair my point is a little pedantic, but it is a tricky rule to write.
And it was always deeply f'n irritating when they scored off the back of that